1. Field of Invention
The present invention relates to a non-volatile memory cell and methods for forming and operating the same. More particularly, the present invention relates to a single-poly electrically erasable programmable read-only memory (EEPROM) cell and methods for forming and operating the same.
2. Description of Related Art
Being affected by the increasing popularity of the consuming electronic products, the non-volatile memory, in which the data and contents are still stored even the power is off, is widely used in various electronic equipments such as multimedia or portable multimedia including digital camera, audio player and cellular phone. Integrating the manufacture of the non-volatile memory with the manufacture of other devices such as CMOS, logic device, high voltage device or low voltage device becomes one of the development tendencies.
Conventionally, the electrically erasable programmable read-only memory (EEPROM) is one kind of non-volatile memory. Typically, an EEPROM cell comprises two stacked gates which include a polysilicon floating gate used for storing charges therein and a polysilicon control gate for controlling the access of the data. Usually, the floating gate is at a floating situation and is not electrically connected to any other circuit. Additionally, the control gate is connected to the word line. Furthermore, the control gate is stacked over the floating gate and is electrically separated from the floating gate with a dielectric layer.
Since the conventional EEPROM possesses two stacked polysilicon gates, the step height of the EEPROM is larger than the step heights of any other single-layer polysilicon devices. Therefore, the difficulty for integrating the manufacture of the EEPROM and the manufacture of the other devices is increased. Besides, in order to integratedly manufacture two-layer polysilicon EEPROM and the single-layer polysilicon devices, the number of masks used in the integrated manufacturing process is increased and the manufacturing process becomes more complicated.